Formula (I) is deemed to define isomers of 2,6-dimethylbicyclo[4.4.0]decan-1-ol, namely the isomers of formula ##STR3##
(-)-Geosmin (Ic), which is a known compound, was isolated for the first time by Gerber et al. [Appl. Micro-biol. 13, 935 (1965)] as a metabolite of several micro-organisms of the family of actinomycetes. It occurs also in nature as a metabolite of certain algae [see T. Kikuchi et al., Chem. pharm. Bull., 21, 2342 (1973)] and it has been considered as the compound responsible for the desagreable odour of public water supplies. Its odour has been defined by most of the authors as being earthy-musty and, so far, no utilization of it has been nor mentioned nor suggested. We have now unexpectedly discovered that (-)-geosmin, as well as its isomers of formula (Ia) and (Ib) possessed very useful odorous properties and, consequently, these compounds could be advantageously used in numerous perfume compositions of various nature.